Hybrid drive having an internal combustion engine with reduced drag torque

ABSTRACT

A hybrid drive for a vehicle includes an electric machine, an internal combustion engine, and a transmission with a transmission input shaft. The electric machine and the internal combustion engine are coupled to the transmission input shaft such that the electric machine and the internal combustion engine cannot be decoupled.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a hybrid drive. In particular the invention relates to a hybrid drive which can be operated with a drag-torque-reducing internal combustion engine.

A vehicle having a hybrid drive comprises an internal combustion engine and at least one electric machine, which can each be used individually and/or together in order to provide a drive torque which is requested at a transmission of the vehicle. In order to reduce the drag torque in the non-activated or activated operating mode having reduced drag torque of the internal combustion engine, one or more drag-torque-reducing measures can be implemented. An exemplary drag-torque-reducing measure is to switch off one or more cylinders of the internal combustion engine.

The reduction in the drag torque of the internal combustion engine permits the non-activated internal combustion engine to be entrained in a way which is efficient in terms of energy, wherein the entrainment of the internal combustion engine in turn permits prompt reactivation of the internal combustion engine in a way which is efficient in terms of energy.

The present document is concerned with the technical problem of providing a hybrid drive which is efficient in terms of installation space, costs and weight and which permits flexible switching over between different operating modes of the hybrid drive in a way which is efficient in terms of energy and time.

It is to be noted that additional features of a patent claim which is dependent on an independent patent claim can form, without the features of the independent patent claim or only in combination with a subset of the features of the independent patent claim, a separate invention which is independent of the combination of all the features of the independent patent claim and which can be made the subject matter of an independent claim, of a partial application or of a subsequent application. This applies in the same way to technical teachings which are described in the description and which can form an invention which is independent of the features of the independent patent claims.

A hybrid drive for a vehicle, in particular for a motor vehicle, is described according to one aspect. The hybrid drive comprises at least one electric machine and one internal combustion engine (e.g., a diesel engine or a gasoline engine). The electric machine can have an operating voltage and/or rated voltage of 70V or less, of 63V or less, or of 50V or less, in particular of 48V. If appropriate, the electric machine can be configured also to use voltage ranges above 50V (if appropriate also in the high voltage range). The electrical energy for operating the electric machine can be obtained from an electrical energy store (e.g., from a lithium-ion-based battery) of the hybrid drive.

The hybrid drive can comprise a transmission with a transmission input shaft. The transmission can be designed to change a transmission ratio between the transmission input shaft and an output shaft of the transmission (e.g., into two or more, or into four or more, or into six or more stages). The output shaft can be coupled, for example, to one or more wheels and/or to an axle of a vehicle. The transmission typically has at least one clutch in order to decouple the transmission input shaft from the output shaft of the transmission and/or from the transmission stages or to couple it thereto. The clutch can be used to change a transmission stage of the transmission in the scope of a shifting process of the transmission.

The transmission is preferably a double clutch transmission. In particular, the transmission can comprise a first clutch which is configured to couple the transmission input shaft to a first component transmission of the transmission. Furthermore, the transmission can comprise a second clutch which is configured to couple the transmission input shaft to a second component transmission of the transmission. In addition, the transmission can comprise one or more shifting elements for coupling the first component transmission or the second component transmission to the output shaft of the transmission. The use of a double clutch transmission permits shifting processes to be carried out without an interruption in the tractive force.

The hybrid drive is embodied in such a way that the electric machine and the internal combustion engine are coupled to the transmission input shaft in such a way that they cannot be decoupled and/or in a fixed fashion. In particular, the hybrid drive can be embodied in such a way that even in the case of sole operation of the electric machine the internal combustion engine is entrained. The hybrid drive therefore does not have a clutch (in particular no engine disconnect clutch) in order to decouple the internal combustion engine from the electric machine. This permits the electric machine to be integrated into the hybrid drive in a way which is efficient in terms of installation space, weight and costs. Furthermore, the entraining of the internal combustion engine makes possible an efficient transition between different operating modes (in particular between an operating mode with a non-activated internal combustion engine and an operating mode with an activated internal combustion engine) of the hybrid drive, since at all times the internal combustion engine has the necessary rotational speed to take up the load.

The hybrid drive can comprise a control unit. The control unit can be configured to determine that the output shaft of the transmission is to be driven by the electric machine but not by the internal combustion engine. In particular it can be determined that the hybrid drive is to be operated in a purely electrical operating mode. In addition, the control unit can be configured to bring about one or more drag-torque-reducing measures in order to reduce a drag torque which is brought about at the transmission input shaft by the internal combustion engine. Exemplary drag-torque-reducing measures are to disconnect one or more cylinders of the internal combustion engine or to adapt the opening angles and/or closing angles of the inlet valves and/or outlet valves of the internal combustion engine. Implementing one or more drag-torque-reducing measures can permit the internal combustion engine to be entrained in the non-energized operating mode in a way which is efficient in terms of energy (wherein the entraining also permits the efficient re-activation of the internal combustion engine).

The transmission can comprise a wet space as part of an oil circuit of the transmission. The wet space can be arranged, for example, in a housing of the one or more clutches of the transmission. The electric machine can be connected to the transmission input shaft in the wet space of the transmission. In particular, a gearwheel for connecting the electric machine can be arranged in the wet space. This makes possible particularly efficient connection of the electric machine since the oil circuit of the transmission can be used to lubricate the connection of the electric machine.

The hybrid drive can comprise a damping system for damping torsional oscillations (e.g., a two-mass flywheel). The crankshaft of the internal combustion engine can be coupled to the transmission input shaft via the damping system, in order to permit low-oscillation operation of the hybrid drive.

In addition, the electric machine can be coupled to the transmission input shaft in such a way that in a purely electric operating mode of the hybrid drive the crankshaft of the internal combustion engine is driven by the electric machine via the damping system. In other words, the electric machine is preferably located in the drivetrain in an arrangement as follows:

internal combustion engine crankshaft, subsequently a damping system, followed by the electric machine. This permits low-oscillation connection of the electric machine.

In addition, in this arrangement the electric machine can be followed by one or more clutches of the transmission which are coupled to the transmission input shaft. In particular the electric machine can be coupled to the transmission input shaft between the damping system and the one or more clutches of the transmission. This makes particularly efficient connection of the electric machine possible.

The electric machine can be coupled to the transmission input shaft via a spur gear stage in a fixed fashion and/or in such a way that it cannot be decoupled. The electric machine can be coupled in a particularly flexible way to the transmission input shaft via a chain in a fixed fashion and/or in such a way that it cannot be decoupled.

According to a further aspect, a (road) motor vehicle (in particular a passenger car or a truck or a bus or a motorbike) is described which comprises the hybrid drive described in this document.

The vehicle can comprise an axle which is driven by the hybrid drive, wherein the electric machine of the hybrid drive is arranged parallel to the driven axle. This can permit installation of a hybrid drive in a way which is particularly efficient in terms of installation space.

It is to be noted that the devices and systems which are described in this document can be used both alone as well as in combination with other devices and systems which are described in this document. Furthermore, any aspects of the devices and systems which are described in this document can be combined with one another in a variety of ways. In particular, the features of the claims can be combined with one another in a variety of ways.

In the text which follows, the invention will be described in more detail with reference to exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary hybrid drive of a vehicle with a double-clutch transmission;

FIG. 2 shows further details of the double-clutch transmission illustrated in FIG. 2; and

FIG. 3 shows an optimized connection of the electric machine of a hybrid drive to a double-clutch transmission.

DETAILED DESCRIPTION OF THE DRAWINGS

As stated at the beginning, the present document is concerned with providing a hybrid drive which is optimized for operation with an internal combustion engine with reduced drag torque. In this context, FIG. 1 shows a block diagram of an exemplary hybrid drive 100 for a vehicle. A hybrid drive 100 comprises an internal combustion engine 101 and an electric machine 102 which can be used individually or together to generate a drive torque for the vehicle. The internal combustion engine 101 and the electric machine 102 are arranged in such a way that the torques generated by the respective drive motor are added together to form an overall drive torque which is transmitted, for example, via a transmission 104 and an output shaft 108 of the transmission 104 to one or more wheels 109 of the vehicle. The electric energy for the operation of the electric machine 102 can be stored in an electrical energy store 110.

The vehicle and/or the hybrid drive 100 also comprise a control unit 111 (e.g., an engine control unit) which is configured to determine a requested overall drive torque. The requested overall drive torque can be specified by a driver of the vehicle by means of an accelerator pedal and/or by means of a setting of the transmission 104, for example. For example, a driver can activate the accelerator pedal to request an increased overall drive torque. The control unit 111 can be configured to divide the requested overall drive torque into a first torque (for the internal combustion engine 101) and into a second torque (for the electric machine 102). In other words, the control unit 111 can be configured to operate the internal combustion engine 101 and the electric machine 102 as a function of a requested overall drive torque.

In the example illustrated in FIG. 1, the hybrid drive 100 comprises a double-clutch transmission 104 which has a first clutch 105 which is configured to couple the transmission input shaft 107 of the transmission 104 to a first input shaft 115 to form a first component transmission 125 of the transmission 104 or to decouple it therefrom. Furthermore, the transmission 104 has a second clutch 106 which is configured to couple the transmission input shaft 107 of the transmission 104 to a second input shaft 116 to form a second component transmission 126 of the transmission 104 or to decouple it therefrom. The transmission input shaft 107 can be coupled directly or indirectly (e.g., via a two-mass flywheel) to the internal combustion engine 101, in particular to the crankshaft of the internal combustion engine 101.

The first input shaft 115 and the second input shaft 116 are typically coaxial with respect to one another. In particular, the first input shaft 115 can be a solid shaft which is encircled by the second input shaft 116 which is embodied as a hollow shaft. The first input shaft 115 can be coupled to the output shaft 108 via the first component transmission 125 and a gear speed which is set therein. Furthermore, the second input shaft 115 can be coupled to the output shaft 108 via the second component transmission 126 and a gear speed which is set therein. For example, the uneven gear speeds (e.g., 1, 3, 5, etc.) can be provided by the first component transmission 125, and the even gear speeds (e.g., 2, 4, 6, etc.) by the second component transmission 126. The first and/or second component transmissions 125, 126 typically have one or more shifting elements 103 by means of which the different gear speeds of the respective component transmission 125, 126 can be engaged in an automated fashion and/or by means of which the respective component transmission 125, 126 can be placed in a neutral position (without a gear speed engaged). In a neutral position the input shaft 115, 116 of a component transmission 125, 126 is typically decoupled from the output shaft 108.

In the example illustrated in FIG. 1, the electric machine 102 of the hybrid drive 100 can be coupled only to one of the two component transmissions 125, 126 or connected to only one of the two component transmissions 125, 126. In particular, the electric machine 102 can be or is coupled directly to the input shaft 115, 116 by one of the two component transmissions 125, 126. Furthermore, the electric machine 102 is arranged in such a way that coupling to the input shaft 115, 116 of the respective other component transmission 125, 126 is possible only via the clutches 105, 106.

FIG. 2 shows further details of the double-clutch transmission 104 which is illustrated in FIG. 1 and has an electric machine 102 which is connected only to the second component transmission 126 of the double-clutch transmission 104. In particular, the electric machine 102 is arranged downstream of the clutches 105, 106 of the double-clutch transmission 104 (which are also referred to as starter elements) so that at least for some of the gear speeds a coupling of the electric machine 102 to the output shaft 108 of the transmission 104 is possible only by closing both clutches 105, 106.

On the other hand, the electric machine 102 is arranged or connected upstream of the output-side shifting elements 103.

The connection of the electric machine 102 illustrated in FIGS. 1 and 2 in a purely electric operating mode of the hybrid drive 100 is disadvantageous, since shifting processes are possible only with interruption of the tractive force and/or by means of assistance from a service break of the vehicle. This has adverse effects on the comfort and/or on the energy efficiency of the hybrid drive 100.

FIG. 3 shows a hybrid drive 100 in which the electric machine 102 is fixedly coupled to the transmission input shaft 107 of the transmission 104. In particular, the electric machine 102 can be connected between the damping system 201 for reducing torsional oscillations (in particular from the two-mass flywheel) and upstream of the starter element 105, 106 (i.e., upstream of the double clutch). It is therefore possible for there to be an efficient and comfortable connection of the electric machine 102. In particular, in this way it is possible to efficiently and comfortably avoid interruptions in the tractive force during shifting processes in the purely electric operating mode.

The connection of the electric machine 102 can be carried out with a chain 303 or by means of a spur gear stage in the wet space 307 of the transmission 104. In particular, a gearwheel 302 which is coupled to a gearwheel 304 of the transmission 104 via a chain 303 in a fixed fashion and/or such that it cannot be decoupled can be arranged on the drive axle 301 of the electric machine 102, wherein the gearwheel 304 is fixedly coupled to the transmission input axle 107 and/or to the primary side 305 of the transmission 104 or is directly connected to the transmission input axle 107 via a toothed engagement of one or more spur gear stages.

The connection between the damping system 201 for reducing torsional oscillations and the starter element 105, 106 forces the coupling to the transmission input shaft 107 to take place in a region in which the irregularity of the rotational speed is already alleviated by the damping system 201, so that this region is advantageous in terms of technical design criteria and in terms of criteria of the acoustics of the vehicle. Furthermore, the connection in the wet space 307 of the transmission 104 permits a common oil circuit to be used for the transmission 104 for the purpose of cooling and lubricating the connection of the electric machine 102.

The electric machine 102 can be arranged axis-parallel to a driven axle of a vehicle, in a way which is efficient in terms of installation space.

The electric machine 102 therefore has a connection to the transmission input shaft 107 which cannot be decoupled, causing the internal combustion engine 101 to be entrained in the purely electric operating mode. In order to reduce the drag torque of the internal combustion engine 101, it is possible to implement one or more drag-torque-reducing measures. For example, one or more cylinders of the internal combustion engine 101 can be switched off. The drag torque which is brought about by the internal combustion engine 101 in the purely electric operating mode can therefore be reduced.

On the other hand, the entraining of the internal combustion engine 101 in the purely electric operating mode is advantageous, since the entraining efficiently permits prompt re-activation of the internal combustion engine 101 to be brought about. In other words, the entraining of the internal combustion engine 101 makes an efficient changeover possible between the different operating modes (purely electric operating mode and operation with a portion provided by an internal combustion engine) of a hybrid drive 100.

The present invention is not limited to the exemplary embodiments shown. In particular it is to be noted that the description and the figures are intended to represent only the principle of the provided devices and systems. 

1.-11. (canceled)
 12. A hybrid drive for a vehicle; comprising: an electric machine; an internal combustion engine; and a transmission with a transmission input shaft; wherein the electric machine and the internal combustion engine are coupled to the transmission input shaft such that the electric machine and the internal combustion engine cannot be decoupled.
 13. The hybrid drive according to claim 12, wherein: the transmission has a wet space as part of an oil circuit of the transmission; and the electric machine is coupled to the transmission input shaft in the wet space of the transmission.
 14. The hybrid drive according to claim 12 further comprising a damping system for damping torsional oscillations; wherein a crankshaft of the internal combustion engine is coupled to the transmission input shaft via the damping system; and wherein the electric machine is coupled to the transmission input shaft such that in a purely electric operating mode of the hybrid drive the crankshaft of the internal combustion engine is driven by the electric machine via the damping system.
 15. The hybrid drive according to claim 12, wherein: the transmission has a clutch, wherein with the clutch the transmission input shaft can be decoupled from an output shaft of the transmission and/or from the transmission; and the electric machine is coupled to the transmission input shaft upstream of the clutch with respect to the output shaft of the transmission.
 16. The hybrid drive according to claim 12, wherein the electric machine is coupled to the transmission input shaft via a spur gear stage in a fixed manner and/or such that the electric machine cannot be decoupled.
 17. The hybrid drive according to claim 12, wherein the electric machine is coupled to the transmission input shaft via a chain in a fixed manner and/or such that the electric machine cannot be decoupled.
 18. The hybrid drive according to claim 12, wherein the electric machine has an operating voltage and/or a rated voltage of 70V or less.
 19. The hybrid drive according to claim 12, wherein: the transmission is a double clutch transmission; the transmission has a first clutch which is configured to couple the transmission input shaft to a first component transmission of the transmission; the transmission has a second clutch which is configured to couple the transmission input shaft to a second component transmission of the transmission; and the transmission has one or more shift elements for coupling the first component transmission or the second component transmission to an output shaft of the transmission.
 20. The hybrid drive according to claim 12 further comprising a control unit configured to determine that an output shaft of the transmission is to be driven by the electric machine but not by the internal combustion engine and to bring about one or more drag-torque-reducing measures in order to reduce a drag torque which is brought about on the transmission input shaft by the internal combustion engine.
 21. A vehicle, comprising: the hybrid drive according to claim
 12. 22. The vehicle according to claim 21, wherein the vehicle has an axle which is driven by the hybrid drive and wherein the electric machine of the hybrid drive is disposed parallel to the axle. 